1. Field of the Invention
The present invention relates to a light source device using a solid-state light-emitting element such as a light-emitting diode (LED), a super luminescence diode (SLD) or a laser diode (LD), and to an image capturing device using the light source device.
2. Description of the Related Art
Conventionally, image capturing devices such as an endoscope, which uses a solid-state image capturing element such as a charge-coupled device (CCD) for converting an optical image into electrical signals, have been utilized in the medical field for capturing an optical image of an observation area. Image data outputted from the solid-state image capturing device have an advantage that a plurality of people can observe the image data simultaneously by means of displaying the data on a monitor or the like. Moreover, the image data can be subjected to a variety of image processing prior to display, whereby it is also possible to display histopathologies on the monitor, which are unrecognizable with the naked eye, thus contributing largely to developments in medical science.
In the endoscope as described above, a light source such as a xenon lamp, a halogen lamp or metal halides (hereinafter collectively referred to as the xenon lamp, etc.) is used to illuminate the observation area. It is possible to irradiate sufficient illumination light onto the observation area by use of the above-mentioned light source.
However, since the above-mentioned light source device including the xenon lamp, etc. is large and expensive, the image capturing device itself becomes large and expensive. Moreover, the illumination light emitted from the above-described light source device contains long-wavelength components such as infrared light. Accordingly, a large amount of heat is generated in a position where the illumination light is irradiated. For this reason, in the endoscope provided with the solid-state image capturing element being disposed at an inserting portion to be inserted into a living body, there is also a problem that dark noise is generated due to the heat and the noise is included in output data, whereby an S/N ratio of an obtained image is deteriorated.